Coal fly ash as a soil conditioner for field crops in southern Ontario

Sixty-eight percent of the 957 000 Mg of fly ash (FA) from coal-fired generating stations in Ontario was landfilled in 1998. Current restrictions by government regulators prevent its use for agricultural purposes. Greenhouse and field experiments were therefore initiated to assess the effects of FA On plant growth. The objective of the greenhouse study was to evaluate various rates of FA (0-80 Mg ha(-1) equivalent) on soil pH, soil and plant nutrient le, eb, and plant growth using representative acidic clay and sandy soils from Southern Ontario. After 90 d of soil incubation, the highest rates of FA. increased sail pH, but had no significant effect on hot-water extractable B. Dry-weights of plants grown in the same soil types were unaffected by FA rates. In a 3-yr field study, Fit was applied to acidic clay and sandy loam soils at rates ranging from 0 to 50 Mg ha(-1) (drg wt. basis). Lime control treatments were also included. In Year 1, corn (Zen mays L) plant emergence, grain yield, percent moisture, and harvest index were not significantly influenced by FA applications. However, soybean [Glycine mar (L)Merr.] yields treated,with 50 Mg ha(-1) FA increased by as much as 35 and 31% in comparison with untreated and lime control treatments, respectively. Selenium and boron, while presently the rate-limiting elements for maximum permissible loading rates of FA for soil amendments in the province, did not accumulate in plants in quantities that would be of concern for plant health or animal and human consumption.